Trump says not after regime change in Iran

US President Donald Trump says he wants to see a strong Iran and is not seeking a change of leadership in Tehran, adding that the standard of living for ordinary Iranians is unacceptable.

"I'm looking at a really good Iran, really strong, we're not looking for regime change. You've seen how that works over the last 20 years, that hasn't been too good," Trump told reporters during a summit of wealthy nation leaders in France on Monday.

He said he had not been surprised that France had invited Iranian Foreign Minister Mohammad Javad Zarif for talks on Sunday on the sidelines of the G7 gathering, which were aimed at trying to ease tensions between Washington and Tehran.

However, he said he had not wanted to see Zarif himself, adding that it was too soon for such an encounter.

"I knew he was coming in and I respected the fact that he was coming in. And we're looking to make Iran rich again, let them be rich, let them do well, if they want," he said.

"Or they can be poor as can be. And I tell you what, I don't think it's acceptable the way they are being forced to live in Iran," he said.

Tensions between Tehran and Washington have risen sharply since Trump pulled out of Iran's internationally-brokered 2015 nuclear deal and reimposed sanctions on the Iranian economy.

"What we want is very simple. It's got to be non-nuclear. We're going to talk about ballistic missiles, we're going to talk about the timing," he said, adding: "But they have to stop terrorism. I think they are going to change, I really do. I think they have a chance."